Substantial amounts of energy are lost during deceleration of propulsion systems. This is particularly true in vehicles where large amounts of kinetic energy is dissipated during slow downs and stops. When braking is used, this energy is normally dissipated as heat.
Over the years various attempts have been made to harness this energy including flywheels into which the energy is transferred during deceleration and is then available for acceleration. Also electric systems have been investigated where the kinetic energy is converted to electricity and stored until needed.
The flywheel concept of storing deceleration kinetic energy has the advantage of being a kinetic energy transfer means but is not a long term storage system since the flywheel itself will decelerate and eventually stop due to friction losses.
Although the electrical storage systems store energy for longer periods of time than the flywheel, they are inefficient and will eventually discharge if not used over an extended period of time.
Rubber bands have, of course, been used in model airplanes and other vehicles as a primary propulsion means but this, first, does not store the energy from deceleration and, secondly, considerable energy is lost due to friction in the twisting and untwisting process. In addition, this friction would render this method of energy storage unacceptable for use in a system of the type disclosed since friction causes excessive wear.